Catholics are a sacramental people. We not only profess our faith through our words, but also through our actions. Gestures made with the body constitute an acknowledgement of God’s presence. We genuflect as a sign of adoration and belief in the Real Presence of Jesus Christ in the Eucharist. We bow as a form of reverence to signify our belief and to give respect for that which we are bowing to.
Genuflection (GIRM 274):
A genuflection, made by bending the right knee to the ground, signifies adoration, and therefore it is reserved for the Most Blessed Sacrament, as well as for the Holy Cross from the solemn adoration during the liturgical celebration on Good Friday until the beginning of the Easter Vigil.
If the tabernacle with the Most Blessed Sacrament is present in the sanctuary, the priest, the deacon, and the other ministers genuflect when they approach the altar and when they depart from it, but not during the celebration of Mass itself. [If the priest has difficulty genuflecting, it is common practice for the priest, deacon and other ministers to make a profound bow instead].
During Mass, three genuflections are made by the priest celebrant: namely, after the showing of the host, after the showing of the chalice, and before Communion.
Otherwise, all who pass before the Most Blessed Sacrament genuflect, unless they are moving in procession.
Usually when people enter a Catholic church and walk to their pew they genuflect before sitting down, which is a small gesture of adoration for the Most Blessed Sacrament. However, it’s important to note that a genuflection is only necessary when passing the tabernacle. This means a person should look out for the tabernacle, as the tabernacle may not be visibly present, in a side chapel, or even empty.
On Good Friday, when the Blessed Sacrament has been removed to the altar of repose, we do not genuflect before the empty tabernacle. A good reminder is to look for the lamp which is kept burning near the tabernacle when the Blessed Sacrament is present.
Bowing (GIRM 275):
Ministers carrying the processional cross or candles bow their heads instead of genuflecting. A bow signifies reverence and honor shown to the persons themselves or to the signs that represent them. There are two kinds of bows: a bow of the head and a bow of the body.
a. A bow of the head is made when the three Divine Persons are named together and at the names of Jesus, of the Blessed Virgin Mary, and of the Saint in whose honor Mass is being celebrated.
b. A bow of the body, that is to say a profound bow, is made to the altar; during the prayers such as, Munda cor meum (Almighty God, cleanse my heart) and in the Creed at the words, “by the power of
the Holy Spirit . . . and became man.” The same kind of bow is made by the deacon when he asks for a blessing before the proclamation of the Gospel. In addition, the priest bows slightly as he speaks the
words of the Lord at the consecration.
(Sources: General Instruction of the Roman Missal, aleteia.org)
Read more in the “Why Do We Do That?” series from Deacon Mike Fritz.